In a conventional paper feeder, when paper stacked in a stacker is picked by a pick roller, paper 54 is arranged to be inserted into a portion between a pick roller 50 and a separation pad 51 and to be transported one sheet at a time into an apparatus by making use of a frictional force, as shown in FIG. 5.
The arrangement provided is such that, to ensure that a sufficient frictional force acts between the pick roller 50 and the separation pad 51 at that time, a pad pressing means 52 is provided which applies a pressing force for causing the separation pad 51 to come into contact with the surface of the pick roller 50 by means of a pressing spring 53 so as to cause the separation pad 51 to contact the pick roller 50.
With such a structure, however, the area where the separation pad 51 comes into contact with the pick roller 50 inevitably becomes small, so that there have been cases where a plurality of overlapping sheets cannot be separated by the separation pad 51, resulting in the occurrence of multi-feeding.
Accordingly, an automatic paper feeder has been devised in which the shape of the pad pressing means 52 for applying a pressing force to the separation pad 51 is formed in a reverse U-shape, whereby the separation pad 51 can be pressed at two portions thereof against the surface of the pick roller 50, making it possible to more reliably separate the sheets one by one (e.g., refer to patent document 1).
Even with such a structure, however, the distribution of pressure applied at two front and rear portions of the pad pressing means 52 is not uniform owing to the contact between the paper 54 and the pad 51, so that there have been cases where the sheets cannot be reliably separated one by one.    Patent document 1: JP-A-8-91609